


Psfck December prompts

by Gallavantula



Category: Undertale (Video Game)
Genre: M/M, Swapfell Papyrus (Undertale), Swapfell Purple, Swapfell Sans (Undertale)
Language: English
Status: Completed
Published: 2019-12-02
Updated: 2020-02-22
Packaged: 2021-02-26 03:54:13
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 3
Words: 3,703
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21647125
Author URL: https://archiveofourown.org/users/Gallavantula/pseuds/Gallavantula
Summary: From the RedTomatoFan and MeGaLoTrash's Pswapfell month kink fills event.Going to try my best to at least hit ten.Warnings and kinks featured in the notes of each chapter.Incest warning. It's going into gross territory.
Relationships: Papyrus/Sans (Undertale)
Comments: 3
Kudos: 20





	1. Chapter 1

**Author's Note:**

> Uniform/Crying kink/ dry humping  
> Day 1  
> NO beta, already a day late lmao

He hadn't meant to time things so poorly. Business was business, and the coin had to come from somewhere as long as it was earned. Lining up a few blowjobs before lunch was supposed to be the norm, but that was before… Cash tried not to think about it. He tried a lot things. Selling corner food, offering postal service. It was offering host services that got him here in the first place. A drink too many here, a lot of flirting there. 

So what if he fucked more clients than he had days on the job? He liked it, they liked it. And he got paid! He could afford his own drugs and Iris didn't have to know. Didn't know. Now that was fucked. Heheh. 

Man it was hard to let his mind wander. 

"PAPYRUS." Came his brother's commanding tone, pushing past the foggy bliss of arousal to jam his thoughts into the same hole he was avidly trying to avoid thinking about. His mouth opened to reply, something snarky from his catalogue of quick dialogue choices was knocked askew as he felt that hot, straining bulge of mana press down against his tailbone again. 

"gnrffhh…" Was Cash's intelligent rebuttle, hitching up with a desperate whimper as the weight on his back pushed him tight to the shack wall, grinding up against every ripple of his tailbone to settle heavy behind his pelvic inlet. Which throbbed for more, for faster, for hotter- And remained aching for it. It. 

Iris chuckled, breathlessly and cruel into the juncture of his jaw and audial cavity. 

"YOU FILTHY SLUT. DISGUSTING." 

Yet his body arched and trembled, shuddering through another swell of arousal. Betrayed. Disgustingly betrayed. He was a slut. If the money was right, he'd let just about anyone fuck him. Apparently, that included Iris. 

"s-sanss-" Cash could feel one of those stupid medal pins scratch the back of his head, and the sting only made his soul slicker against his ribcage as he felt something, maybe an arm push down against his waist. Like he was being arrested, maybe--Iris was currently on duty as a royal guardsmen-

"DO YOU FEEL IT? HOW YOU GRIND UP AGAINST ME? HOW HIGH ARE YOU, BROTHER?" The accusations only made his knees shake harder, knocking together against the edge of the crate at his feet. He did. His head was swimming with the implications, the weight of how against the rules, against the uniform his brother wore this was. Every touch of those buttons or bunched satin slacks against his bones eeked this up until finally his magic gave up and snapped into a throbbing passage. Even Iris could only gasp in shock, surprised, even as Cash felt a coil tighten through his being at how perfectly wide that trapped cock felt. 

"gnh-g'nna arrest me-?" Laugh wheezing like that would only earn more ire, and the grip around his collar only tightened when he felt it be pulled back. That's it, bad cop. Rough me up- Boy this is not the time. 

"YOU'RE LUCKY I DON'T." Came the stern, utterly reserved warning, and Cash the roiling energy through his being pitch forwards. Even the punishing jut of an elbow into his back only made his clit throb against the inseam of his shorts, seeping through the thin material. He hoped it stained those dressy clothes, marred Iris' stern authoritative figure--

"hhnnff-" Close, fuck he was so close and sensitized already. How pathetic, to be brought to this state so suddenly. A dark snarl echoed, and with a swift shift beneath Cash, his pelvis was suddenly supported against a formed, taunt knee. Unbidden he ground down into it, feeling that smear of pollen from his weeping style as it flowered open for every brush. He could pretend this was anyone else, pretend it was a gross, smarmy client and- The distraction fails when Iris adjusts, dry humping his body into the thin shack wall like he may just break them both. 

It was so Iris to be overzealous, no matter what. Perhaps the laugh he made was breathless, it was probably utterly manic, but it made fingers dig into his mouth to shut him up. Oh, the scandal, if someone caught them like this. The need for his throbbing opening to be plowed and filled brought wet, suckling whimpers out of Cash until Iris had to hiss against his jaw with another bite. 

"WHAT'S A MATTER WITH YOU, SLUT?" That word again. He felt another glob drip from his soul and smother down his ribcage with a moist, smothering feeling that bordered into too much. 

"mn-or'-" He begged, utterly shameless as the tears sparkling around his eyelights finally shed. There was no turning back, not that he'd want to. How many times had the danced around one another? How many times would he have to pretend? This, he decided, would be one less. 

"CRYING- REALLY?" Iris sounded ashamed, annoyed--but even Cash could feel how fervent those bumping grinds into his tailbone got once the next set started. A sob weakly made it past those fingers, stunned into twitching like a busted doll until finally his clit was pinched between their bodies and he came, gurgling around the mana surging up his throat and through those measly shorts. The aftershocks burn through thought and morality, crumbling at his judgement and sinking him another step closer to depravity. 

In the haze, all he can make out is Iris angrily complaining, moving a hand between them to cup the sopping wet mess leaving a sweetly lavender stain. 

"-DIRTIED MY UNIFORM-..!"


	2. Day 2: Choking

**Summary for the Chapter:**

> Cash likes to think he's smart.  
> Iris is always smarter.   
> Warning for potential non-con vibes.

**Notes for the Chapter:**

> Warning for potential non-con vibes.

It has to be a trap, his mind screamed again. Big red flags, Cash. There's no way Iris would just forget a bottle of pills like this. Yet there they sat, pristine and white, atop the fridge. Cash tried in vain to ignore it, to pretend he was just grabbing another beer from the cooler but… His withdrawal throbbed. His bones begged. 

So he looked closer, dipped his head left and right. No strings, from what he can see. Grabbing a stool, he stood atop it perilously to look for some sort of sensor or colour that would tip him off to a trap, but nothing. 

This has to be a trap.   
There's no way it's just been left out in the open like this. Cash could swear his ecto began to shiver, mana begging to form and do something about the sweat building up, fudging the line between reason and temptation. 

Deliberately and gently, he hefted the broom handle and wobbled it above the bottle to trigger something, and then tapped the bottle itself with the end before flinching back. Yet nothing happened. 

A streak of magic sweat dribbled into the rim of his scarred socket, and the spike in his pulse was enough. Thrown aside, the broom clattered too loudly as he jumped up from the stool, making to swipe the bottle before regrets could stop him. His hand felt the plastic, and bliss filled his thoughts at the relief they would bring before suddenly, bones formed and barred him from moving any further. His arm hit the side of the construct, stinging enough that he yelped, wobbled and crashed into the fridge with a clamour. 

The bottle of beer was forgotten and smashed to the floor, creating a horrible mess that would incriminate him further if he wasn't already panicked by being caught. Fuck! 

“fuuuck-!" Why hold back now, when the damage was done? His instincts had been right! It was a trap! Like a trapped animal he braced his feet to the door, heaving in hopes of bringing his hand back through the bars before he felt the pinch on his mana lines and whimpered, feet sliding down into the pooling mess on the floor just to keep his arm in it's socket. Great. Great! 

"I SEE THE NAUGHTY BIRD WASN'T QUITE AS SMART AS IT THOUGHT IT WAS." 

Chilled to the core, Cash began a nervous giggle as he turned, looking at his brother like he could weasel his way out of this. The mandible began working, words tumbling on the end of his tongue, but Iris wasn't amused by any of it. What a mess… With a displeased grimace, his heavy boots began to carry forward, crunching broken glass beneath his soles. 

An eep escaped, and Cash fumbled to stand again like the height difference could change anything. 

"-so let me go, asshole. ain't exactly rocket science, you set me up-" Mouthy, too. Sneering, Iris reached in to grab his throat, nearly bashing the back of his skull against the fridge before leaning in to crush off any more air. Startled, his brother could do little more than flail and kick, struggling to gain purchase on the armour there to push back. An arm looped in beneath his chin, but Iris was used to more fight than this. 

"I DIDN'T ASK YOU. WHAT I DID ASK, WAS FOR YOU TO STOP MAKING A NUISANCE OUT OF YOURSELF." With ease, his magic crackled and brought a piece of glass into his hand. That single eyelight in Cash's socket flared and looked directly at it, gulping the small tube of ecto against his spine like he needed to swallow at all. How cute… The glass is held closer towards his parted teeth, as if threatening to place it inside Cash's mouth. 

"WHEN I RELEASE YOU, YOU'RE GOING TO DO SOMETHING ABOUT THIS. OR, I'LL MAKE SURE EVERY SHARD IS PICKED UP BY YOUR MOUTH, MY STEEL TOE DIGGING INTO YOUR BACK FOR EVERY INCH YOU MISS." 

The threat of course, is for show. He knows his brother will clean up. But the tension between them is what riles him up, pushing that dark edge closer and closer. And apparently, when a small wet snap of magic hit the air, so did Cash. The skeleton's face ignited lavender, the swallows more desperate around his gloved fingers as he tilted to hide himself. 

Oh, how too late it all was. Greedily, Iris leaned in to inhale the smell of his magic sweat, a knee tilting up to rub against the formed cock he'd found there. Adorable. Iris' face drew up at the sides, his grin only growing more terrifying by the second as his sockets darkened. Devouring every breath that Cash grew more desperate, hands punching and pinching at his body to try and escape. A shove to his chin, a trembling hand cupping his cheek, but it had no strength to make Iris budge. The delirium in that eyelight grew to sparkling delight, rasping wetly until finally Iris released him. 

Then, Cash was wheezing and nearly drooling, hand up to protect his neck as the other unhelpfully tugged his pants around. As if it could hide that vibrant colour, that addicting uncertainty to his face that melded a tense discomfort in his bones. Instead, he looked more roughed up than before, sockets slanted in an expression of betrayal. Seems even pushing a soft spot wasn't enough to derail him, and Iris' features schooled into something aggressive and sufficiently menacing. 

"fuck you." Eloquent as ever, the thinner skeleton stuck out his tongue, and then suddenly ported into his movement line in a flash.


	3. After Care (Day 3)

**Summary for the Chapter:**

> Day 3 on that kink list. A most special thank you to Redtomatofan for her support and inspiration. 
> 
> Cash is in an unfortunate spotlight and it does change how Iris feels about him.

Even Cash wasn't so sure how it progressed this far, this differently from the norm. He could hear the coffee contraption in the kitchen bubbling, so Iris had to be home. First instinct is to steer his thoughts away from it, questioning instead what time it was. His entire body had been sleeping moments before, but something woke him out of nowhere. Thoughts circled around that stupid, oversized, outdated machine Iris loved so much, it was enough to help him turn over, pointed edge and misaligned rib at a time before he could squint into the dark. Fuck he felt sore… Something throbbed behind his head, jagged and rough like a broken bottle but he ignored it to decipher the blurry, blocky letters of his alarm clock. It told him it was 10:03. The relevance of such an hour did not click until the gears caught one another and began to turn. Was this a hangover..? But it's the middle of the week-

He'd slept in?? How? Unsteady, he got to his feet, listening for signs of heavy boots or the radio… Yet nothing appeared outside the static noise in his own head. Uhg… Work probably went poorly last night; as if it could have gone any differently, forced to be without his usual cocktail. A sock lost in sleep, Cash hobbled with his bare foot favoured to lean into the door, slowly turning the knob to keep it from alerting his brother. Outside everything was still. Even as he carefully moved the door inch by inch, he felt his bones aching from the effort. Might be time to take another dose, fight off the withdrawal for another few hours- 

A soft sigh paralyzed his progress. Honing what skill Cash had, he hesitated and waited for another sign. Where did it come from? Indecision held on until a beading of sweat slid down between the cushions of his spine. Owch, okay, time to risk it. The door hung ajar enough for Cash to slide his leg forward, leaning down onto his toes as the ache jolted up into every cushioned segment it had. 

The wince nearly had a whimper, but he was stronger than that. Stronger than this, than whatever was hurting him enough to make this a chore. Fuck… Maybe allowing himself to be tied up for his customers had been a bad choice… No time to regret it now, though another step forward onto the mezzanine spiked more unpleasant buzzing into his pelvis. 

Okay, maybe he could regret it when he felt the flooring shift, and though it had been nearly silent-

"PAPYRUS. BACK TO BED. THAT'S AN ORDER." 

Fuck's SAKES-

"an if i don't?" 

Iris sat up from the couch at last, revealing his location. The coffee machine continued to sizzle and steam from the kitchen, filling the atmosphere with a heady aroma as eyelights met. All the snark left Cash just as easily as he noted every detail in his brother within seconds. The wrinkles in his uniform, the missing badges and untied scarf hung loose around his unbuttoned collar. Even his gloves were gone, hanging limply from his side pocket… 

Iris looked fierce all the same, posture wide and shoulders rolled back like he was ready to keep fighting, to argue his authority into Cash's stubbornness. Yet he could almost smell the staleness of his clothes, and though his soreness was lingering and making things annoyingly curt, it was easy to piece together that his hard ass brother hadn't slept a wink. 

"I'LL TIE YOU DOWN AGAIN." Even as he spoke it, his tone did not hide the raw vulnerable anger that snapped behind it. It made Cash realize that his little soirée last night wasn't a secret, and the missing spots had answers he was uncomfortable knowing existed. Iris had seen. Probably felt how his bones had been exposed and tugged on, the scratches and gouges inflicted for maximal stimulation. Their eyelights never left one another, but the current of emotions made Cash sick. 

"don't." Is his rasped answer, already leaning back into the door frame for stability as shame ate behind his sockets. Fuck. Fuck. Iris wasn't supposed to know how bad it was, how bad he is- Even as Iris began to move, dully stepping on the carpet with slippers of all things, Cash could barely hold back the raw animal from lashing out. 

"IF YOU DON'T GET BACK IN THERE, I CAN'T GUARANTEE HOW HAPPY YOU'LL BE WITH ME." A plain warning without games or insinuations. An olive branch. Yet as soon as he took the first step up, Cash felt his soul fluttering with further panic. 

"don't you fuckin dare-" Was he screechy? Everything hurt more than he was happy with, and even stepping back only made the cushion of his legs wobble and unsettle him. He can't run like this, either. He can't hide. His hand moved to shut the door, but Iris was there with a sudden heavy step and yanked it open again, hitting the wall with a nasty crack. 

"STOP FIGHTING ME, PAPYRUS!" His grip was always iron strong, but it felt cool and warm all at once. Bone on bone had never felt so good, and the jack rabbit seemed to settle into a trembling ball inside Cash's chest as he glared falteringly at his brother. 

"why??" He snarled back, baring teeth that had nothing on Iris' perfect, gorgeous canines--Worriedly his gaze shot back up to stained sockets, and the sudden waft of coffee jittered a nervous laugh. Iris rarely drank so much. Had he been up all night-? "so you can throw me into another prison? so you can control me?" 

The hold tightened, and the pain there was bliss compared to the pounding in his pelvis, in his joints. It was so much easier to keep Iris out if he fought him, kept him at bay. Better to anger the guard dog than try to make friends. Yet, Iris simply yanked Cash forward into him, meeting stiff canvas and a shoulder before he was picked up behind the knees. 

"wuh-" Nothing could be done other than to yell again, small fist banging on Iris' back as he was casually carried back into his despondent room. "fuck off, Sans! let me down."

"FINE." He was prepared to be thrown down or discarded, left to the disgusting state of his disorders and avoidance. Yet another hit to Iris' shoulder did little to stall or encourage. Instead, he was gently leaned back to lay down, only dropping at the last moment into his cushions and sheets with minor discomfort. The softness had Cash leer up at his brother, his tormentor, hoping to push him away before he could come in close. It was too late for that, as Iris remained above him, eyes burning serious and bright triangles that brooked for nothing more. 

"STAY." 

Vehemently, Cash pushed everything up into his voice to lace the venom there. 

"no." 

The stare he received helped little. Laid out like this, he felt pinned like a specimen, exposed and empty for Iris to read his every ugly mistake. His magic roiled against his ribcage, soul pounding up against his clavicle that he felt ready to spit it out at that expression his brother wore. Those sockets were hooded, sure, but there was nothing dark or violent about them. No leering, no judgement. Eyelights flickered, bit here and there, stalemate on opposing forces as Cash continued to swallow down his self preservation instincts. 

"Stay." Iris said again, gently fluffing the pillows beneath Cash and worked to tuck him in with gentle touches and a firm swipe down along the topmost sheets to smother his bones with that soft, silky warmth. At first, Cash felt like an invalid, jaw articulating various words he meant to barb himself with, before that face hovered a breadth from his own. 

"You have been relieved from today's duties." Iris said, careful and casual, as if the boring of those eyelights were anything but penetratingly acute. 

"no i ain'-" 

"AND I-" Iris snapped sharply, fangs in dazzling display that only made Cash's body feel horrendously warmer. Fuck. Damnit! Even his squirming was doing little other than wrinkle his sheets at this point. "-AM going to watch over your recovery."

The stare he gave, utterly shocked, must have done something to soften his brother's gaze because he doesn't stop the small half smirk from forming as he reached up for an errant eye patch to tug down with gentle care. "Yes, even I can take days off." 

"...but you…" Cash tried to insist, to argue, to prevent his hardened soul from going soft as a delicate talon brushed down along his nasal ridge to secure the elastic. It's freaking him out how caring and careful he was being, roiling uncertainty beneath his ribcage as he felt the weight shift and more of that larger, stronger body lie in next to his. Even their legs met, and his raspy shudder couldn't be bit back fast enough. Iris heard how vulnerable he was. 

"Your drug was tampered with. I'm making sure you don't suffer any ill effects." Ahh… That explains a lot of his current symptoms, actually. Threw his magic right off… And that headache, buzzing like glass behind his sockets. Uhg. It would be much easier to rest, ease himself back into slumber. Cash was never one for the easy way out of anything, and stubbornly he persisted to resist it. No. His gaze looked to Iris, who shifted a little more to support his head on his crooked arm, eyelights scoping out his expression with that attention to detail… Nervously Cash gulped on nothing. 

"what are you doing?" His voice trembled, tight wired and unable to trust in anything so simple. Iris merely hummed, and gently adjusted the blanket up a little tighter. 

"... Helping." Iris answered softly, uncertainty pulling his brow together. The entire scenario was absurd, even as he half snorted and nestled his head down into the pillow. What the fuck was this, some bastardization of aftercare? Cash rolled his eyelight for it, scoffing before it died when the aroma of coffee returned. Iris had been up all night. He never does that.

"heh… don' let me waste yer energy…" 

A grunt of disagreement is made, yet he doesn't move away, instead setting his arm over top of his ribcage that he could feel the warmth there. How active Iris' mana was, so close to his own… Cash sighs, already feeling even weaker than before. His head was so heavy, and soon his socket did too. A rumbling started, soft and subtle, gently stirring his senses with another passing breath of coffee. His ability to remain prickly and resistant to comfort failed entirely as the sound of Iris purring finally clouded his thoughts. 

Before long, Cash was asleep, finally at rest even as Iris sighed in relief. 

"Honestly, Papyrus…"


End file.
